Image formation apparatus with printer engine control which judges whether recording sheets can be fed

ABSTRACT

An engine control unit and corresponding method of controlling the engine in which the engine control unit receives a print reservation command for plural pages prior to a print request command from a printer control unit. When the engine control unit received the print reservation command for the plural pages, it is judged whether or not a sheet feed operation of recording sheets can be performed. When it is judged that the recording sheets can be fed, the recording sheets are fed and transported to a predetermined position on a transportation path with a minimum constant interval corresponding to the sheet size by sheet feed rollers or transportation rollers, then printing operation is performed according to the print request command.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an image formation apparatus of anelectrophotographic system and a control method thereof.

2. Related Background Art

Conventionally, an image formation apparatus is composed of a printercontroller which develops image code data transmitted from an externalequipment such as a host computer or the like into bit data necessaryfor printing to be performed by a printer and reads internal informationof the printer to display the information, and a printer engine controlunit, of which an operation is controlled according to an instructionfrom the printer controller, notifies the internal information of theprinter to the printer controller.

In case of performing printing on the basis of image data transmittedfrom the external equipment, the print controller which develops theimage data executes a print instruction to the engine control unit, andthe engine control unit which received the print instruction feedssheets which are on a predetermined sheet feed cassette (a sheet feedtray) through a sheet feed port. When a printable state is prepared byperforming initialization of an electrophotographic process, printing isexecuted on the basis of the image data transmitted from the externalequipment while taking a synchronization in a vertical direction(synchronization between image writing to a photosensitive drum andpaper feeding) with the printer controller.

In case of continuously printing plural pages, the print controllerperforms printing operation one page by one page in such order of atransmission of the print instruction, a vertical synchronization, atransmission of the print instruction of a second page and a verticalsynchronization of the second page.

However, in the above conventional image formation apparatus, since itis structured that a sheet feed operation of a next page can be startedafter terminating vertical synchronization processing of the fed sheet,a page interval becomes longer in an image formation apparatus having along sheet feed transportation path. Therefore, there occurred a problemthat the capacity of a maximum throughput essentially possessed by anapparatus itself can not be efficiently exhibited.

SUMMARY OF THE INVENTION

The present invention has been made to solve the above problem, and anobject is to provide an image formation apparatus which can maximumlyexhibit the capacity of the maximum throughput essentially possessed bythe apparatus itself without increasing the cost and a control methodthereof.

A representative of the image formation apparatus and the control methodthereof according to the present invention is an image formationapparatus of an electrophotographic system, comprising:

a sheet feed means for feeding recording sheets one by one;

a transportation means for transporting the recording sheets fed by thesheet feed means to a position where a visualized image formed on aphotosensitive drum is transferred to the recording sheet, through atransportation path;

an engine control unit for controlling drives of the sheet feed meansand the transportation means; and

a printer control unit for developing image data and transmitting aprint request command to the engine control unit,

wherein the engine control unit has judgment means for judging whetheror not the recording sheets can be fed when a print reservation commandfor plural pages of the sheets was received from the printer controlunit prior to the print request command, and the drives of the sheetfeed means and the transportation means are controlled to transport therecording sheets to a predetermined position on the transportation pathwhen the judgment means judges that the recording sheets can be fed.

Preferably, a serial communication is performed between the enginecontrol unit and the printer control unit.

Preferably, when it is designated that the sheets are fed from pluralsheet feed ports according to the print reservation command for pluralpages, the drives of the sheet feed means and the transportation meansare controlled to transport the recording sheets from the plural paperfeed ports to the lowest-stream position capable of performing printingin order of a print reservation for the plural pages prior to the printrequest command.

Preferably, when it is designated that the recording sheets are fed fromthe plural sheet feed ports according to the print reservation commandfor the plural pages, the drives of the sheet feed means and thetransportation means are controlled to transport the recording sheetsfrom the plural sheet feed ports to a stream position more upper than ajunction of the most-upper-stream on the transportation path in case offeeding the sheets from the plural sheet feed ports prior to the printrequest command.

Preferably, when it is designated that the recording sheets are fed fromthe plural sheet feed ports according to the print reservation commandfor the plural pages, there equipped a mode for controlling the drivesof the sheet feed means and the transportation means to transport therecording sheets from the plural sheet feed ports to the lowest-streamposition capable of performing printing in order of the printreservation for the plural pages prior to the print request command, amode for controlling the drives of the sheet feed means and thetransportation means to transport the recording sheets from the pluralsheet feed ports to a stream position more upper than the junction ofthe most-upper-stream on the transportation path in a case where thesheets were fed from the plural sheet feed ports prior to the printrequest command, and selection means for selecting one of the bothmodes.

An image formation apparatus of another aspect according to the presentinvention being the image formation apparatus of the electrophotographicsystem, comprises:

a sheet feed means for feeding recording sheets one by one;

a transportation means for transporting the recording sheet fed by thesheet feed means to a transference means for transferring a visualizedimage formed on a photosensitive drum to the recording sheet, through atransportation path;

an engine control unit for controlling drives of the sheet feed meansand the transportation means; and

a printer control unit for developing image data and transmitting aprint command for issuing a print instruction and a print reservationcommand for previously instructing print information such as a sheetfeed port, sheet size or the like prior to the print command, to theengine control unit through a serial communication line,

wherein the engine control unit has judgment means for judging whetheror not a sheet feed operation of the recording sheets can be performedwhen the print reservation command for plural pages was received fromthe printer control unit, and when the judgment means judged that therecording sheets can be fed, drives of the sheet feed means and thetransportation means are controlled to transport the recording sheets toa predetermined position on the transportation path.

Preferably, plural sheet feed means are equipped, and the transportationmeans can be driven or stopped in driving of the transference means,

the predetermined position on the transportation path is more upper thanthat of the transference means, and a leading edge of the recordingsheet is on the lowest-stream position from where the sheet is nottransported to the transference means when the transportation means isstopped, and

the drives of the sheet feed means and the transportation means arecontrolled to feed and transport the recording sheets to thepredetermined position on the transportation path in order of receptionof the print reservation command, when the engine control unit receivesthe print reservation command for plural pages to be fed from the pluralsheet feed means from the print control unit.

Preferably, plural sheet feed means are equipped, and each of the sheetfeed means can be driven or stopped in driving of the transportationmeans,

the predetermined position on the transportation path is more upper thanthat of a junction where a transportation path of another sheet feedmeans is interflowed, and a leading edge of the recording sheet is onthe lowest-stream position from where the sheet is not transported tothe junction when the sheet feed means is stopped, and

the drives of the sheet feed means and the transportation means arecontrolled to feed and transport the recording sheets to thepredetermined position on the transportation path from all of the sheetfeed means reserved in the print reservation command, when the enginecontrol unit receives the print reservation command for plural pages tobe fed from the plural sheet feed means from the print control unit.

Preferably, when the engine control unit received the print reservationcommand for the plural pages to be fed from the plural sheet feed meansfrom the print control unit, there equipped selection means which canselect one of control means from first control means for controlling thedrives of the sheet feed means and the transportation means to feed andtransport the recording sheets to the predetermined position on thetransportation path in order of reception of the print reservationcommand and second control means for controlling the drives of the sheetfeed means and the transportation means to feed and transport therecording sheets to the predetermined position on the transportationpath from all of the sheet feed means reserved in the print reservationcommand.

A control method of an image formation apparatus of anelectrophotographic system according to the present invention,comprises:

a sheet feed step of feeding recording sheets one by one from sheet feedmeans;

a transportation step of transporting the recording sheets fed by thesheet feed means to a transference means for transferring a visualizedimage formed on a photosensitive drum to the recording sheet, through atransportation path;

an engine control step of controlling drives of the sheet feed step andthe transportation step by an engine control unit; and

a printer control step of developing image data and transmitting a printcommand for issuing a print instruction and a print reservation commandfor previously instructing print information such as a sheet feed port,sheet size or the like prior to the print command, to the engine controlunit through a serial communication line by a printer control unit,

wherein the engine control unit judges whether or not a sheet feedoperation of the recording sheets can be performed when the printreservation command for plural pages is received from the printercontrol unit, and when it is judged that the recording sheets can befed, drives of the sheet feed means and the transportation means arecontrolled to transport the recording sheets to a predetermined positionon the transportation path.

Another image formation apparatus according to the present invention,comprises:

an image formation means for forming images on recording sheets;

a sheet feed means for feeding the recording sheets;

a transportation means for transporting the recording sheets fed by thesheet feed means to the image formation means through a transportationpath;

an engine control unit for controlling drives of the sheet feed meansand the transportation means; and

a reception means for receiving a print request command transmitted froma printer control unit and a reservation command used in reservingprinting prior to the print request command,

wherein the engine control unit has judgment means for judging whetheror not the recording sheets for pages corresponding to print reservationcan be fed, and the plural recording sheets can be fed before receivingthe print request command in accordance with a judgment of the judgmentmeans in a case where the print reservation for plural pages is made byusing the reservation command.

Preferably, plural sheet feed means are equipped, and at least one ofthe sheet feed means and sheet size can be instructed every therecording sheet of each page corresponding to the print reservation fromthe printer control unit.

Preferably, when the print reservation for plural pages to use theplural sheet feed means is made, printing is performed in order of themade print reservation, and the recording sheets are fed every pagecorresponding to the print reservation at timing of corresponding toinformation related to the recording sheets of pages previously printreserved.

Preferably, when the print reservation for the plural pages to use theplural sheet feed means is made, printing can be performed in anarbitrary order for the print reserved plural pages, and when the printreservation for the plural pages to use the plural sheet feed means ismade, the engine control unit controls to feed and transport therecording sheets every the sheet feed means to be used to anupper-stream position of a junction, where a transportation path fromthe sheet feed means joins a transportation path from another sheet feedmeans.

Preferably, when the print reservation for the plural pages to use theplural sheet feed means is made, there equipped selection means whichselects one of a first mode for performing printing in order of the madeprint reservation and a second mode for performing printing in anarbitrary order for the print reserved plural pages.

According to the present invention, a high speed image formation can berealized in the image formation apparatus of the electrophotographicsystem. Even if the transportation path of the recording sheets isdesigned to have a long path, an achievement of the maximum throughputcan be easily realized without increasing the cost.

Other objects and features of the present invention will become apparentfrom the following detailed description and the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a longitudinal cross-sectional diagram showing the structureof a printer according to a first embodiment;

FIG. 2 is a block diagram showing the circuit structure of a controlsystem of the printer according to the first embodiment;

FIG. 3 is a diagram indicating timing between a print command and avertical synchronization according to the first embodiment;

FIG. 4 is a flow chart showing a sheet feed control operation accordingto the first embodiment;

FIG. 5 is a longitudinal cross-sectional diagram showing the structureof a printer according to a second embodiment;

FIG. 6 is a block diagram showing the circuit structure of a controlsystem of the printer according to the second embodiment;

FIG. 7 is a flow chart showing a processing operation from a printreservation to a print execution according to the second embodiment; and

FIG. 8 is a diagram showing the constitution of a print reservationcommand and a print command according to the second embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, the embodiments of the present invention will be explainedin detail with reference to the attached drawings. In the embodiment, anexample of a printer will be explained among image formationapparatuses.

(First Embodiment)

FIG. 1 is a longitudinal cross-sectional diagram showing the structureof a printer according to the first embodiment. In FIG. 1, numeral 101denotes a photosensitive drum being an electrostatic latent imagesupport body. Numeral 102 denotes a semiconductor laser unit serves as alight source. Numeral 103 denotes a rotative polygon mirror rotated by ascanner motor 104. Numeral 105 denotes a laser beam which is irradiatedfrom the semiconductor laser unit 102 and scans a surface of thephotosensitive drum 101.

Numeral 106 denotes a charge roller which uniformly charges the surfaceof the photosensitive drum 101. Numeral 107 denotes a developing unitwhich develops an electrostatic latent image formed on thephotosensitive drum 101 using a toner. Numeral 108 denotes a transferroller which transfers a toner image developed by the developing unit107 to a predetermined recording sheet. Numeral 109 denotes a fixingunit which thermally fixes the toner transferred to the recording sheet.

A cassette sheet feed roller (sheet feed means) 110 feeds sheets from acassette having a function of discriminating a size of the recordingsheet and sends the recording sheet to a transportation path by onerotation. A manual sheet feed roller (sheet feed means) 111 sends therecording sheets from a manual tray not having the function ofdiscriminating the size of the recording sheet to the transportationpath through a sheet feed port. An option cassette sheet feed roller(sheet feed means) 112 sends the recording sheets from a detachableoption cassette having the function of discriminating the size of therecording sheet to the transportation path. An envelope feeder sheetfeed roller 113 (sheet feed means) sends the recording sheets one by onefrom a detachable envelope feeder capable of stacking only the envelopesto the transportation path. Transportation rollers 114 and 115(transportation means) transport the recording sheets fed from thecassette or the option cassette.

A prefeed sensor 116 detects a leading edge and a trailing edge of thefed sheet. Pre-transfer rollers 117 (transportation means) send thetransported sheet to the photosensitive drum 101. A top sensor 118 takesa synchronization (vertical sync) with image writing(recording/printing) to the photosensitive drum 101 and a sheettransportation for the transported sheet and measures length of the fedsheet in the transporting direction. A sheet discharge sensor 119detects presence/absence of the sheet, to which fixing processing wasexecuted. Sheet discharge rollers 120 discharge the sheet, to which thefixing processing was executed, to the outside of the apparatus.

A flapper 121 switches a transport destination (discharge to a tray, ora detachable two-faced processing unit) of the printed sheet.Transportation rollers 122 (transportation means) transport the sheet,which is transported to the detachable two-faced processing unit byswitching the flapper, to a reverse unit. A reverse sensor 123 detects aleading edge and a trailing edge of the sheet transported to the reverseunit. A sheet refeed roller 124 (sheet feed means) reverses the sheet bysequentially performing a rotation/reverse rotation operation and sendsthe sheets to a sheet refeed unit.

FIG. 2 is a block diagram showing the circuit structure of a controlsystem for controlling such a mechanism as described above. In FIG. 2, aprinter controller 201 (a printer control unit) develops image code datatransmitted from an external equipment such as a host computer (notshown) or the like into bit data required in printing and readsinformation in a printer to display it.

A printer engine control unit 202 controls an operation of each sectionof a printer engine according to an instruction from the printercontroller 201 and notifies the information in the printer to theprinter controller 201. A sheet transportation control unit 203 performsdrive/stop operations of motors, rollers and the like used in feedingand transporting the recording sheets according to an instruction fromthe printer engine control unit 202. A high voltage control unit 204performs a control of each high voltage output in each step ofdischarging, developing, transferring or the like according to theinstruction from the printer engine control unit 202.

An optical system control unit 205 controls the drive/stop operations ofthe scanner motor 104 and the lighting of the laser beam according tothe instruction from the printer engine control unit 202. A fixing unitcontrol unit 207 performs the drive/stop operations of power conductingto a fixing heater according to the instruction from the printer enginecontrol unit 202.

A sensor input unit 206 according to the prefeed sensor 116, the topsensor 118, the reverse sensor 123 or the like notifies thepresence/absence of the sheets in the cassette and the presence/absenceof the sheets in the transportation path to the printer engine controlunit 202.

A detachable option cassette control unit 208 performs the drive/stopoperations of a driving system according to the instruction from theprinter engine control unit 202 and notifies the presence/absence of thesheets and sheet size information to the printer engine control unit202.

A control unit 209 of the detachable two-faced processing unit reversesthe sheet, performs a sheet refeed operation according to theinstruction from the printer engine control unit 202 and simultaneouslynotifies the above state to the printer engine control unit 202.

A detachable envelope feeder control unit 210 performs the drive/stopoperations of the driving system according to the instruction from theprinter engine control unit 202 and notifies the presence/absence of thesheets to the printer engine control unit 202.

Between the printer controller 201 and the printer engine control unit,a 16-bit serial communication is performed. For 16-bit command datatransmitted from the printer controller 201, the printer engine controlunit 202 retransmits information in the engine as 16-bit status data inaccordance with the command contents. Furthermore, processing ofperforming an operation according to the command contents is executed.

The printer controller 201 can transmits at least two kinds of 16-bitcommand data of a print reservation command and a print command to theprinter engine control unit 202. The print reservation command ispreviously transmitted to the printer engine control unit 202 prior tothe print command. For example, a command code system of the printreservation command may be same as that of the second embodiment (FIG.8) described later or may be such a form which does not contain a job IDin each of 12th to 15th bit codes shown in FIG. 8. In case of containingthe job ID, the printer controller 201 transmits the command data to theprinter engine control unit 202 by adding an ID number in order of pagesto be printed later according to the print reservation command. In thiscase, for example, such a constitution of performing a cancellation ofthe reservation by specifying the job ID is applicable. It should benoted that it may be constituted that a reservation regarding therecording sheets already fed is not to be canceled. The engine controlunit 202 which received the command performs sheet feed andtransportation operations in order of the reserved ID from a designatedsheet feed port. For example, when the print reservation command isreceived in a state that the sheet feed port is designated for acassette having a function of discriminating the size of the recordingsheet, one of the sheets stacked on the cassette is picked up byrotating the sheet feed roller 110, and then the picked up sheet istransported by driving the transportation rollers 114 and 115. When theprefeed sensor 116 detects a leading edge of the transported sheet,drives of the transportation rollers 114 and 115 are stopped to stop thetransportation of the sheets. Accordingly, the leading edge of the sheetfed and transported from the cassette is fed and transported to apredetermined position between the prefeed sensor 116 and thepre-transfer rollers 117.

The print command is transmitted to the printer engine control unit 202from the printer controller 201 which terminates to develop printingdata received from the external equipment such as the host computer (notshown) or the like into bit map data. The printer engine control unit202 which received the print command starts the scanner motor and thefixing unit and initializes an electrophotographic process. When it isterminated to initialize the electrophotographic process, the drives ofthe transportation rollers 114 and 115 are restarted, and thetransportation of the sheet, which was fed and transported to thepredetermined position when the print reservation command was received,is restarted. Thereafter, at a time point when the top sensor 118detected the leading edge of the sheet, printing operation is startedwhile taking a vertical direction synchronization with the printercontroller 201.

In case of continuously printing plural pages, the print controller 201transmits the print command of a follower sheet to the printer enginecontrol unit 202 after performing a vertical synchronization of aprecedent sheet. The print command of the follower sheet can not betransmitted prior to a vertical synchronization signal. For example, asshown in FIG. 3, with respect to the print command and a verticalsynchronization, the printer controller 201 transmits the print commandof the follower sheet synchronizing with the vertical synchronization inorder of the print command for a first sheet, the verticalsynchronization for the first sheet, the print command for a secondsheet and the vertical synchronization for the second sheet. On thecontrary, the print reservation command for plural pages can betransmitted non-synchronized with the vertical synchronization. In thepresent embodiment, in a case where the print reservation for pluralpages to use the plural sheet feed ports is made, printing is performedin order of the made print reservation.

FIG. 4 is a flow chart showing a control sequence of a sheet feedoperation of the printer engine control unit 202 which received theabove plural print command. It should be noted that this operation isperformed by an instruction from a CPU (not shown) on the basis of aprogram stored in a ROM (not shown).

First, in a step S101, it is confirmed whether or not the printreservation command is received from the printer controller 201. In caseof not receiving the print reservation command, a reception of the printreservation command is always observed. The printer engine control unit202 which received the print reservation command in the step S101 startsa sheet feed operation of feeding the sheets from the cassette, themanual tray and the envelope feeder which are designated from theprinter controller 201 in the step S101, through each sheet feed port.In a case where the sheet feed port is not designated, a default sheetfeed port held by the engine when the power is turned on or a sheet feedport designated by the just before reservation is set. Designation ofthe sheet feed port is performed by outputting a sheet feed portdesignation command or a recording sheet size designation command fromthe printer controller 201 prior to the print reservation command. Incase of the latter command, a sheet feed port capable of feeding therecording sheet of designated size is set.

Then, in a step S103, an operation of a timer for measuring a sheet feedinterval used in judging whether or not a sheet feed operation of thefollower sheet can be performed, is started. When the precedent sheet isstopped to be fed, this timer stops the operation during the stoppedperiod. In a step S104, an increment for a counter, which confirms thenumber of the sheets in feeding the sheets, is performed.

If printing operation is performed for one sheet, since the printercontroller 201 transmits the print reservation command only one time,the printer engine control unit 202 does not identify the printreservation command for the follower sheet in a step S105, and theprefeed sensor 116 detects the leading edge of the sheet in a step S111,thereby performing a decrement for the counter which confirms the numberof the sheets in feeding the sheets in a step S112 to confirm that thecounter indicates “0” in a step S113, then the sheet feed operation isterminated.

In case of performing printing for plural pages, since the printercontroller 201 transmits the print reservation command for these pages,a reception of the print reservation command for the follower sheets isconfirmed in a step S105. In the step S106, the printer engine controlunit (judgment means) 202 which received the print reservation commandfor the follower sheets confirms a timer value of the timer of whichoperation is started in the step S103, and it is confirmed whether ornot the sheet feed operation of the follower sheets is in possibletiming of performing that operation. The timer value for the start ofthe sheet feed operation differently varies according to the size of theprecedent sheet and the sheet feed port of the precedent sheet or thefollower sheet, and references the start of the sheet feed operation ofthe precedent sheet so as to achieve the maximum throughput byperforming the sheet feed operation of realizing a minimum constantinterval corresponding to the sheet size. When the precedent sheet isstopped, since the timer stops its operation during the stopped period,when reaching a timer value for the start of the sheet feed operation ofthe follower sheet before the precedent sheet reaches a predeterminedposition, the sheet feed operation of the follower sheet is alsostarted, and the both recording sheets are transported. On the otherhand, even if the precedent sheet reaches the predetermined position,when not reaching the time value for the start of the sheet feedoperation of the follower sheet, the follower sheet is to be fed afterthe print command for the precedent sheet is received. Therefore, sheetfeed timing of the follower sheet related to the reservation is suchtiming which corresponds to the presence/absence of the precedent sheet,the sheet feed port, transporting state and the sheet feed port of thefollower sheet.

In the step S106, if the sheet feed operation of the follower sheet isin the possible timing of performing that operation, a timer operationfor the precedent sheet is terminated in a step S107, and the sheet feedoperation of the follower sheet is started in a step S108. Then, in astep S109, an initial value is set to the timer for measuring the sheetfeed interval used in judging whether or not the sheet feed operation ofa next follower sheet can be performed, then the operation of the timeris started, and perform the increment for the counter which confirms thenumber of the feed sheets in a step S110.

In case of printing plural pages, controls from the step S105 to thestep S113 are repeated, and all the sheet feed operations are terminatedin a step S114 by confirming that a counter for counting the number ofthe feed sheets indicates “0”.

As described above, in the present embodiment, in case of printing theplural pages, if the sheet feed operation of the follower sheet is inthe possible timing of performing that operation, the sheets are to befed and transported to the predetermined position on the transportationpath with the minimum constant interval corresponding to the sheet sizewithout waiting for the termination of vertical synchronizationprocessing of the fed sheets. Therefore, the image formation can beperformed at a high speed, and an achievement of the maximum throughputcan be easily realized without increasing the cost even if thetransportation path is designed to have a long path.

(Second Embodiment)

FIG. 5 is a longitudinal cross-sectional diagram showing the structureof a mechanism of a printer according to the second embodiment. In FIG.5, numeral 1201 denotes a photosensitive drum on which an electrostaticlatent image is formed. Numeral 1202 denotes a charge roller whichuniformly charges a surface of the photosensitive drum 1201. Numeral1205 denotes an optical unit which scans the surface of thephotosensitive drum using a laser beam. Numeral 1206 denotes the laserbeam which is irradiated from the optical unit 1205. Numeral 1203denotes a developing unit which develops the electrostatic latent imageformed on the photosensitive drum 1201 by the laser beam, using a toner.

Numeral 1204 denotes a transfer roller charge unit which transfers atoner image on the photosensitive drum 1201 to a predetermined sheet.Numeral 1207 denotes a fixing unit which melts the toner on the sheet tofix it to the sheet. Numeral 1208 denotes sheet discharge rollers whichdischarge the sheet, to which the fixing processing was executed, to theoutside of an apparatus.

A cassette (No. 1) 1209 stacks the sheets to be moved to a sheet feedport No. 1. A cassette No. 1 sheet presence/absence sensor 1210 detectspresence/absence of the sheets in the cassette (No. 1) 1209. A sheetfeed roller (No. 1) 1211 feeds the sheets in the cassette (No. 1) 1209on the basis of an instruction from an engine control unit. Atransportation roller (No. 1) 1212 transports the sheets, which arestarted to be fed by the sheet feed roller (No. 1) 1211, to atransportation path.

A cassette (No. 2) 1213 stacks the sheets to be moved to a sheet feedport No. 2. A cassette No. 2 sheet presence/absence sensor 1214 detectspresence/absence of the sheets in the cassette (No. 2) 1213. A sheetfeed roller (No. 2) 1215 feeds the sheets in the cassette (No. 2) 1213on the basis of an instruction from an engine control unit 302. Atransportation roller (No. 2) 1216 transports the sheets, which arestarted to be fed by the sheet feed roller (No. 2) 1215, to atransportation path.

A cassette (No. 3) 1217 stacks the sheets to be moved to a sheet feedport No. 3. A cassette No. 3 sheet presence/absence sensor 1218 detectspresence/absence of the sheets in the cassette (No. 3) 1217. A sheetfeed roller (No. 3) 1219 feeds the sheets in the cassette (No. 3) 1217on the basis of an instruction from the engine control unit. Atransportation roller (No. 3) 1220 transports the sheets, which arestarted to be fed by the sheet feed roller (No. 3) 1219, to atransportation path.

Numeral 1221 denotes a sheet tray which is used to set the sheets to amanual sheet feed port No. 4. A sheet feed roller (No. 4) 1222 feeds andtransports the sheets from the sheet tray 1221 to the inside of theapparatus.

Numeral 1223 denotes oblique transfer correction rollers which correctan oblique transfer of the sheet. Numeral 1224 denotes a resist rollersensor which takes a synchronization with a transportation of the fedsheet and starting of writing an image to the photosensitive drum 1201.Numeral 1225 denotes a sheet discharge sensor which judges whether ornot the sheet is normally discharged from the fixing unit. Numeral 1226denotes a facedown discharge tray which is used to stack the dischargedsheets.

In a sheet transportation system of the present embodiment, a junctionof the sheet feed port No. 1 and the sheet feed port No. 2 is indicatedby a junction A, and a junction of the sheet feed port No. 2 and thesheet feed port No. 3 is indicated by a junction B.

FIG. 6 is a block diagram showing the circuit structure of a printercontrol system according to the second embodiment. In FIG. 6, numeral301 denotes an image controller (a printer controller) which develops animage code signal from a host computer into bit map data, instructs acommand to the engine control unit 302 through a serial communicationline, performs a control of status reading, and outputs printing data tothe engine according to an image timing signal. Numeral 302 denotes theengine control unit which controls each section of the engine on thebasis of an instruction on the serial communication from the imagecontroller 301.

Numeral 303 denotes a print reservation sheet feed/transportationcontrol unit which is in the engine control unit 302 controls totransport the sheet corresponding to a reserved job to a position wherea printing operation can be performed in order of a job designated by aprint command even if the print command to be instructed after thereservation differs from the reservation order considering a printreservation command from the image controller and a junction of thetransportation system. Numeral 304 denotes a sheet transportationcontrol unit which directly drives a mechanism used in feeding andtransporting the sheets on the basis of an instruction from the printreservation sheet feed/transportation control unit 303.

Numeral 305 denotes an optical system control unit which drives eachfunction unit of an optical system such as a scanner motor, a laser unitor the like on the basis of the instruction from the engine controlunit. Numeral 306 denotes a high voltage system control unit whichcontrols a high voltage unit operating on each electrophotographicprocess of charging, developing or transferring. Numeral 307 denotes afixing unit temperature control unit which controls the temperature ofthe fixing unit on the basis of the instruction from the engine controlunit 302.

Numeral 308 denotes a sheet presence/absence sensor input unit whichnotifies information of the presence/absence of the sheets in thecassette and the presence/absence of the sheets in the transportationpath to the engine control unit 302 and the print reservation sheetfeed/transportation control unit 303. Numeral 309 denotes a jamdetection unit which detects abnormality on transporting the sheets.Numeral 310 denotes a breakdown detection unit which detects thebreakdown of the fixing unit, a scanner unit or the like.

Next, the function of an interface between the image controller 301 andthe engine control unit 302 will be explained.

Numeral 311 which denotes a command/status line in a serialcommunication is an interactive signal line for a signal /SC. Numeral312 denotes a serial clock /SCLK for the serial communication. Numeral313 denotes a vertical sync signal /TOP for taking a synchronizationwith an image output and the sheet transportation. Numeral 314 denotes ahorizontal sync signal /BD for taking a synchronization with a rotationof the scanner motor and the image output. Numeral 315 denotes an imagesignal /VDO to be developed into bit map data by the image controller301 and output from the image controller 301 synchronized with eachsignal /BD.

FIG. 7 is a flow chart showing processing operation (protocol) from aprint reservation to a print execution according to the secondembodiment. It should be noted that this operation is performedaccording to an instruction from a CPU (not shown) on the basis of aprogram stored in a ROM (not shown). In the present embodiment, when theprint reservation for plural pages of using the plural sheet feed portsis made, it is possible to perform printing in an arbitrary order forthe print reserved plural pages.

First, a designation related to the sheet feed port and a sheetdischarge port is received from the image controller 301 (S201). If thedesignation is not received, a default sheet feed port held by theengine when the power is turned on is set.

In this state, upon receiving the print reservation command from theimage controller 301, the print reservation command is stored into theengine control unit 302 together with an ID number which reserved thesheet feed and the sheet discharge from the sheet feed/discharge ports,the sheet size of the sheet feed port and the like. In case of intendingto reserve a different job by changing the sheet feed/discharge ports,the image controller 301 may issue the print reservation command afterinitially resetting a sheet feed/discharge ports designation command(S202). In this manner, the image controller can reserve plural jobs,which also includes jobs of different sheet feed/discharge ports, beforestarting the printing operation.

The image controller 301 can reserve sequential jobs after terminatingthe reservation of all the jobs (S203) or performing the printingoperation which reserved a certain job. An explanation of FIG. 7indicates the former case. The engine control unit 302 judges that thesheets can be transported to what position on the transportation pathbased on information of the sheet feed/discharge ports and the sheetsize of the reserved job after terminating the reservation of the job(S204).

For example, when the job reservation is made by the following order of{job 1 (sheet feed port No. 1, sheet discharge F/D (facedown sheetdischarge), sheet size A4)}, {job 2 (sheet feed port No. 3, sheetdischarge F/D (facedown sheet discharge), sheet size B5)}, and {job 3(sheet feed port No. 2, sheet discharge F/D (facedown sheet discharge),sheet size A4)}, the sheet feed of the job 1 is performed to a forwardposition (upper-stream) of the junction A in FIG. 5, the sheet feed ofthe job 2 is performed to a forward position of the junction B, and thesheet feed of the job 3 is performed to a forward position(upper-stream) of the junction B (S205).

By transporting the sheets to the above position, even if the job isrequested by an order different from the reserved order such as an orderof job 3, job 1 and job 2 (S206), each printing operation can beperformed without inviting any trouble (S207). Furthermore, since thesheets are previously transported to a transportable position, athroughput in printing can be improved.

FIG. 8 is a diagram showing the constitution of the print reservationcommand and the print command according to the second embodiment.

The print reservation command has the 16-bit data structure in which theupper 10-bit data indicates the print reservation command, and the lower4-bit data indicates an ID number of the print job. The ID numbercorresponds to the print command described later, and when the job ofthe reserved ID code is to be performed, the image controller 301 canperform the job by instructing the same ID number by the print command.

Furthermore, according to designation of the command from the imagecontroller 301, in case of performing the print reservation and theprint execution explained in the above first embodiment in the sameorder (first-in, first-out), it is possible to structure that a sheetfeed mode capable of extracting the maximum throughput in reserving theprinting and a mode explained in the second embodiment can be selectedby selection means (not shown).

In this manner, by structuring that the both modes can be designatedfrom the image controller 301, it is possible to cope with a requestfrom the image controller flexibly.

(Other Embodiments)

The present invention is applicable to a system composed of pluralequipments (e.g., a host computer, an interface equipment, a reader, aprinter and the like) or to an apparatus including a single equipment(e.g., a copying machine or the like).

It is needless to say that the object of the present invention can beachieved in a case where a storage medium storing the program codes of asoftware for realizing the functions of the above-described embodimentsis supplied to a system or an apparatus an then a computer (or CPU orMPU) in the system or the apparatus reads and executes the program codesstored in the memory medium.

In this case, the program codes themselves read from the storage mediumrealize the functions of the embodiments, and the storage medium storingsuch the program codes constitute the present invention.

The storage medium for supplying the program codes can be, for example,a floppy disk, a hard disk, an optical disk, a magnetooptical disk, aCD-ROM, a CD-R, magnetic tape, a non-volatile memory card, a ROM, or thelike.

It is needless to say that the present invention also includes not onlythe case where the functions of the embodiments are realized by theexecution of the program codes read by the computer, but also a casewhere an OS (operating system) or the like functioning on the computerexecutes all the process or a part thereof according to the instructionsof the program codes, thereby realizing the functions of theembodiments.

Further, it is needless to say that the present invention furtherincludes a case where the program codes read from the storage medium areonce stored in a memory provided in a function expansion board insertedin the computer or a function expansion unit connected to the computer,and a CPU or the like provided in the function expansion board or thefunction expansion unit executes all the process or a part thereofaccording to the instructions of such program codes, thereby realizingthe functions of the embodiments.

The present invention is not limited to the above embodiments, but maybe modified in various manners within the scope of the following claims.

What is claimed is:
 1. An image formation apparatus of anelectrophotographic system, comprising: sheet feed means for feedingrecording sheets one by one; transportation means for transporting therecording sheets fed by said sheet feed means to a position where avisualized image formed on a photosensitive drum is transferred to therecording sheet, through a transportation path; an engine control unitfor controlling drives of said sheet feed means and said transportationmeans; and a printer control unit for developing image data andtransmitting a print request command to said engine control unit,wherein said engine control unit has judgment means for judging whetheror not the recording sheets can be fed when a print reservation commandfor plural pages of the sheets was received from said printer controlunit prior to the print request command, and the drives of said sheetfeed means and said transportation means are controlled to transport therecording sheets to a predetermined position on the transportation pathwhen said judgment means judges that the recording sheets can be fed. 2.An apparatus according to claim 1, wherein a serial communication isperformed between said engine control unit and said printer controlunit.
 3. An apparatus according to claim 1, wherein when it isdesignated that the recording sheets are fed from plural sheet feedports according to the print reservation command for plural pages, thedrives of said sheet feed means and said transportation means arecontrolled to transport the recording sheets from the plural sheet feedports to the lowest-stream position capable of performing printing inorder of a print reservation for the plural pages prior to the printrequest command.
 4. An apparatus according to claim 1, wherein when itis designated that the recording sheets fed from plural sheet feed portsaccording to the print reservation command for the plural pages, thedrives of said sheet feed means and said transportation means arecontrolled to transport the recording sheets from the plural sheet feedports to a stream position more upper than a junction of themost-upper-stream on the transportation path in case of feeding thesheets from the plural sheet feed ports prior to the print requestcommand.
 5. An apparatus according to claim 1, wherein when it isdesignated that the recording sheets are fed from plural sheet feedports according to the print reservation command for the plural pages,there is set a mode for controlling the drives of said sheet feed meansand said transportation means to transport the recording sheets from theplural sheet feed ports to the lowest-stream position capable ofperforming printing in order of the print reservation for the pluralpages prior to the print request command, a mode for controlling thedrives of said sheet feed means and said transportation means totransport the recording sheets from the plural feed ports to a streamposition more upper than a junction of the most-upper-stream on thetransportation path in a case where the sheets were fed from the pluralsheet feed ports to the print request command, and selection means forselecting one of the both modes.
 6. An image formation apparatus of anelectrophotographic system, comprising: sheet feed means for feedingrecording sheets one by one; transportation means for transporting therecording sheets fed by said sheet feed means to a transference meansfor transferring a visualized image formed on a photosensitive drum tothe recording sheet, through a transportation path; an engine controlunit for controlling drives of said sheet feed means and saidtransportation means; and a printer control unit for developing imagedata and transmitting a print command for issuing a print instructionand a print reservation command for previously instructing printinformation such as a sheet feed port, sheet size or the like prior tothe print command, to the engine control unit through a serialcommunication line, wherein said engine control unit has judgment meansfor judging whether or not a sheet feed operation of the recordingsheets can be performed when the print reservation command for pluralpages was received from said printer control unit, and when saidjudgment means judged that the recording sheets can be fed, drives ofsaid sheet feed means and said transportation means are controlled totransport the recording sheets to a predetermined position on thetransportation path.
 7. An apparatus according to claim 6, whereinplural sheet feed means are equipped, and said transportation means canbe driven or stopped in driving of said transference means, wherein thepredetermined position on the transportation path is more upstream thanthat of said transference means, and a leading edge of the recordingsheet is on a more downstream position from where the sheet is nottransported to said transference means when said transportation means isstopped, wherein the drives of said sheet feed means and saidtransportation means are controlled to feed and transport the recordingsheets to the predetermined position on the transportation path in orderof reception of the print reservation command, when said engine controlunit receives the print reservation command for plural pages to be fedfrom said plural sheet feed means from said print control unit.
 8. Anapparatus according to claim 6, wherein plural sheet feed means areequipped, and each of said sheet feed means can be driven or stopped indriving of said transportation means, wherein the predetermined positionon the transportation path is more upper than that of a junction where atransportation path of another sheet feed means is interflowed, and aleading edge of the recording sheet is on the lowest-stream positionfrom where the sheet is not transported to the junction when said sheetfeed means is stopped, wherein the drives of said sheet feed means andsaid transportation means are controlled to feed and transport therecording sheets to the predetermined position on the transportationpath from all of said sheet feed means reserved in the print reservationcommand, when said engine control unit receives the print reservationcommand for plural pages to be fed from said plural sheet feed meansfrom said print control unit.
 9. An apparatus according to claim 6,wherein when said engine control unit received the print reservationcommand for the plural pages to be fed from said sheet feed means fromsaid print control unit, there equipped selection means which can selectone of control means from first control means for controlling the drivesof said sheet feed means and said transportation means to feed andtransport the recording sheets to the predetermined position on thetransportation path in order of reception of the print reservationcommand and second control means for controlling the drives of saidsheet feed means and said transportation means to feed and transport therecording sheets to the predetermined position on the transportationpath from all of said sheet feed means reserved in the print reservationcommand.
 10. A control method of an image formation apparatus of anelectrophotographic system, comprising: a sheet feed step of feedingrecording sheets one by one from sheet feed means; a transportation stepof transporting the recording sheets fed by said sheet feed means to atransference means for transferring a visualized image formed on aphotosensitive drum to the recording sheet, through a transportationpath; an engine control step of controlling drives of said sheet feedstep and said transportation step by an engine control unit; and aprinter control step of developing image data and transmitting a printcommand for issuing a print instruction and a print reservation commandfor previously instructing print information such as a sheet feed port,sheet size or the like prior to the print command, to the engine controlunit through a serial communication line by a printer control unit,wherein the engine control unit judges whether or not a sheet feedoperation of the recording sheets can be performed when the printreservation command for plural pages is received from the printercontrol unit, and when it is judged that the recording sheets can befed, drives of said sheet feed means and said transportation means arecontrolled to transport the recording sheets to a predetermined positionon the transportation path.
 11. An image formation apparatus comprising:image formation means for forming images on recording sheets; sheet feedmeans for feeding the recording sheets; transportation means fortransporting the recording sheets fed by said sheet feed means to saidimage formation means through a transportation path; an engine controlunit for controlling drives of said sheet feed means and saidtransportation means; and reception means for receiving a print requestcommand transmitted from a printer control unit and a reservationcommand used in reserving printing prior to the print request command,wherein said engine control unit has judgment means for judging whetheror not the recording sheets for pages corresponding to print reservationcan be fed, and the plural recording sheets can be fed before receivingthe print request command in accordance with a judgment of said judgmentmeans in a case where the print reservation for plural pages is made byusing the reservation command.
 12. An apparatus according to claim 11,wherein plural sheet feed means are provided, and at least one of saidsheet feed means and sheet size can be designated for every recordingsheet of each page corresponding to the print reservation from theprinter control unit.
 13. An apparatus according to claim 12, whereinwhen the print reservation for plural pages to use said plural sheetfeed means is made, printing is performed in order of the made printreservation.
 14. An apparatus according to claim 13, wherein therecording sheets are fed every page corresponding to the printreservation at timing of corresponding to information related to therecording sheets of pages previously print reserved.
 15. An apparatusaccording to claim 12, wherein when the print reservation for the pluralpages to use said plural sheet feed means is made, printing can beperformed in an arbitrary order for the print reserved plural pages. 16.An apparatus according to claim 15, wherein when the print reservationfor the plural pages to use said plural sheet feed means is made, saidengine control unit controls drives to feed and transport the recordingsheets by the sheet feed means to an upstream position at a junction,where a transportation path from said sheet feed means joins atransportation path from another sheet feed means.
 17. An apparatusaccording to claim 12, wherein when the print reservation for the pluralpages to use said plural sheet feed means is made, selection meansselects one of a first mode for performing printing in order of the madeprint reservation and a second mode for performing printing in anarbitrary order for the print reserved plural pages.
 18. An apparatusaccording to claim 11, further comprising said printer control unit. 19.An apparatus according to claim 18, wherein said printer control unithas means for developing image code data transmitted from an externalequipment to bit data necessary for an image formation.
 20. An apparatusaccording to claim 11, wherein said image formation means has means forforming an image on an image support body using an electrophotographicmethod and transference means for transferring the image formed on theimage support body to the recording sheet.